Robotics/Exotic Robots/Modular and fractal robots
A robot is generally designed for one particular activity, or at best a few closely related activities. This of course isn't the ideal situation as many jobs require a large number of very different activities. For example, building the walls of a house and installing plumbing and electricity require very different tools and techniques. In practice this means you'll end up designing either several different robots or a very complicated one.
Modular robotics is one answer to such problems. Typical modular robots consist of a number of independent cubes, which can move and connect themselves in many different ways. Each of the cubes have their own power supply and intelligence and can have specific tools. When a problem is fed to its computer, it analyzes it and connects the cubes in such a way that it can solve the problem.
Ideally such a robot would consist of a very large number of very small identical cubes. This is similar to the way plants, animals or humans are consisting of many cells, which are practically identical, with the difference that specification would happen in software rather than in chemical composition.
The difference between fractal and modular robotics is that the former allows multiple sizes of cubes and the latter does not.
Most people are familiar with the fact that sufficient quantities of clay bricks (architectural bricks) or Lego bricks can be used to approximate nearly any shape, and so our introduction to modular robotics was in terms of cubes. Instead of making each cube independent, some researchers make pairs or triplets of cubes independent. However, some roboticists point out that rhombic dodecahedron are, in some ways, superior to cubes.
The open-source ARGoS robot simulator can be used to simulate large heterogeneous swarms of robots.
Many people have built physical prototypes of modular robots.
- MIT Distributed Robotics Lab wiki: "The Self-Reconfiguring Robotic Molecule"
- "Rhombic Dodecahedron Shape for a Self-Assembling Robot" by Mark Yim, John Lamping, Eric Mao, J. Geoffrey Chase. (1997 ?)
- David Christensen, David Brandt, Kasper Stoy, and Ulrik Pagh Schultz. "A Unified Simulator for Self-Reconfigurable Robots".
- GitHub: unified simulator for self-reconfigurable robots; Unified Simulator for Self-Reconfigurable Robots (USSR) at the USD Modular Robotics Research Lab wiki.
- "Self Reconfigurable Modular Technology"
Further reading 
- USD Modular Robotics Research Lab wiki
- ANAT modular robotic technology
- Molecubes For Everyone wiki
- hplusroadmap wiki: "matter compiler"
- "SuperBot" at ISI USC ( Information Sciences Institute of University of Southern California)
- "M-TRAN (Modular Transformer)" at AIST and Tokyo-Tech
- REPY-1 modules: open-source design
- "Modular robotics & Robot locomotion Group" at the School of Mechanical and Production Engineering, Nanyang Technological University.
- "Formica: Affordable, open source swarm robotics"